Sony PlayStation is advising customers to tighten password security and keep a watchful eye on bank account statements following a PlayStation Network security breach and a week's worth of downtime.

PlayStation believes that data obtained during the April 17-19 breach includes names, land and email addresses, birthdates, usernames, passwords, and answers to additional security questions.

The company "cannot rule out the possibility" of credit card information having been taken - numbers and expiration dates, but not the additional security codes found on the back of cards.

"When the PlayStation Network and Qriocity services are restored, we strongly recommend that you log on and change your password," advises the company in a note posted to PlayStation websites and emailed to PSN users.

"Review your account statements," "monitor your credit or similar types of reports" and "be especially aware of email, telephone, and postal mail scams that ask for personal or sensitive information," the note continues.

Christopher Boyd, a senior threat researcher for IT security firm GFI Software, told Relaxnews that the breach was "extremely serious" and that Sony had "no option but to go into full damage control mode" by shutting off the network following discovery of the intrusion on April 20.

"Keeping an eye out for unauthorised payments on credit and debit cards is a good idea for all users, but it's crucial that anybody reusing passwords across multiple accounts changes all their logins to be on the safe side."

One preferred method for choosing a new password involves taking a favorite phrase and making the first letters from each word the basis for the password. Additional numbers and symbols can be introduced for further security.

PlayStation expects "to restore some services within a week," wrote Patrick Seybold, senior director of Corporate Communications, on April 26.